1. Field of the Invention
This invention relates to a device for providing instant hot water at a hot water outlet in a home water plumbing system.
2. Description of Related Prior Art
A great deal of water and heating energy are wasted in waiting, after a hot water faucet or other tap is turned on, for the temperature of the water to rise to the temperature provided by a hot water heater. It has been estimated that about 5000 gallons of water per year are so wasted in the average home. When cold water is drained from hot water pipes, additional cold water enters the hot water heater and must be heated. The energy required for heating such wasted water is considerable.
Numerous prior art devices have been developed for providing instantaneous hot water at a hot water tap, for example in residential plumbing systems. In general, such prior art devices comprise expensive and complicated equipment for such purpose.
For example, Peters, U.S. Pat. No. 2,842,155 discloses a device for providing instantaneous hot water at a hot water faucet by interconnecting the hot and cold water lines and permitting a thermally-induced circulation of hot water into the cold water line. The Peters device comprises a control means 25 interconnecting the hot and cold water lines below the faucets. Means 25 comprises a pipe-like housing 27 which is attached at either end to the hot and cold water lines, and a bypass valve 35 which is seatable against and movable away from valve seat 37 under the action of a thermostatic element 31 responsive to water temperature, thus permitting or preventing the flow of hot water through an orifice 39. Cold water is prevented from entering the hot water line by pressure of cold water exerted on a ball valve 43 positioned in a cage 44 and forcing valve 43 against a valve seat 41 formed on cage 44. Thus Peters requires a thermostatically controlled Bourdon tube 80 that depends on the temperature of the hot water to expand and close a plunger 70. Hot water is maintained at a given point by using a pressure and temperature differential. The Peters device will function only as long as hot water is being purged through the hot water side of the faucet. After hot water has been purged, and the faucet is closed, a cooling effect takes place. The Bourdon tube contracts and closes plunger 70. The cross connection is sealed, and thus there is no convection and the hot water line will cool back to the hot water heater. The only time that the Peters device delivers hot water is after the first purge of hot water (approximately 3-5 gallons). It will maintain hot water for approximately 30 minutes only.
Chubb U.S. Pat. No. 1,108,550 has, as a primary use, the warming of waste water in traps under sinks and bath tubs. Such use no longer applies in modern home construction and plumbing systems.
Chubb U.S. Pat. No. 1,247,374 also discloses a device for preventing freezing of a water distribution system, wherein the hot and cold water lines are interconnected by means of an automatic valve 36 or 36a. Valve 36 is connected at either end to the hot and cold water lines. Mounted within the valve 36 are valve elements 50 and 51, connected by a rod 52 extending through a restricted passageway 48, and biased by springs 56 and 57. In the closed position of the faucets, springs 56 and 57 are so biased that they keep the elements 50 and 51 spaced from the openings to passageway 48 so that hot water can pass into the cold water line. If a faucet is opened, the flow of water is such as to cause element 50 or 51 to compress the respective biasing springs and to close the passageway 48, preventing water from passing therethrough. The Chubb device is designed to work on relatively low temperatures and pressures. Modern high technology, high efficiency water heaters would damage the Chubb device and render it inoperable.
Paulson U.S. Pat. No. 3,543,836 discloses a device for providing instantaneous hot water comprising a pipe 10 interconnecting the hot and cold water lines and forming a closed loop which contains a pump 9 which, on activation, circulates cooled hot water from the hot water line to the cold water lines. The pump is activated by a thermostat 16 positioned in the pipe 10 upstream of the pump and downstream of the connection to the hot water supply line. A signal, equal to the temperature sensed by the thermostat, is transmitted to a temperature controller 17 via a capillary tube 18. Thus Paulson requires a temperature controller to operate a pump on a temperature drop creating a part time delivery of hot water. The device depends on a fan blowing air over a coil to reduce temperature of hot water being moved to the cold water source. The Paulson device is designed for trapped plumbing systems only, so its application is limited. Moreover, the Paulson device in very expensive and is not practical in today's modern systems; it would not be allowed under the plumbing codes of many areas of the United States which prohibit a 110 volt controlling device to be installed under sinks in bathrooms because of the danger of electrical shorts causing injury.
Zimmer U.S. Pat. No. 4,331,292 relates to an instantaneous hot water supply system and comprises a pipe 20 interconnecting the hot and cold water lines. Mounted in pipe 20 is a temperature sensor 15 comprising a U-shaped bimetallic element 17, the free end of which carries a seal 20. Depending upon the temperature in the hot leg of the pipe 20, seal 20 moves into or out of sealing engagement with an orifice 19, permitting or preventing flow of hot water into the cold leg of the pipe 20. A check valve 21 prevents cold water from flowing from the cold leg into the hot leg of pipe 20. Thus, Zimmer requires a thermostatic control device to open or close a seated ball. This device is limited in use and would not apply in a trapped system. A build up of lime deposits on the U-shaped bimetallic member would render it inoperable.
Robillard U.S. Pat. No. 4,672,990 discloses another device for freeze protection of water lines exposed to extreme cold temperatures. This devices requires a mixing tank to receive hot water pumped through a hot water plumbing system through a cross connection. It also requires a thermostatic controller and a remote valve. This system is costly and would waste energy. Lime deposits inside the mixing tank would cause the device to be inaccurate and cause the pump to run longer and waste energy.
Britt U.S. Pat. No. 5,105,846 is directed to an instant hot water system comprising a purge line 25 connected to the hot and cold water lines in which there is provided a pump 28 which can be periodically actuated, e.g. by a timer, to discharge a slug of cool water in the hot water line into the cold water line. A check valve 29 prevents cold water from flowing into the hot water line while allowing water from the hot water line to pass into the cold water line. Thus, Britt requires the use of a third, purge, line to be installed at the back fixture, and a pump. Such an installation is expensive and, practically, Britt is limited to new, modern slab type plumbing systems.
Pegg U.S. Pat. No. 5,135,021 discloses an instantaneous hot water device having a body which is cast in bronze, using a sand core and molding plate. This requires several matching processes to manufacture and is very costly. The device uses a mixing chamber to cross connect the hot and cold water lines through a conduit. In this device it is imperative that the mixing chamber be purged of air or the device will not work. This is done through an air bleed screw. The chamber also becomes a shock absorber and transmits a loud thump when a cold water faucet is opened, causing a pressure drop. Construction is such that installation in close spaces is a problem.
There is a need for an instantaneous hot water device of simple construction, easy to install and of low cost.